I am trying to solve for a simple wave equation using the Pdesolve function. However, it returns an error saying "This variable is undefined". I made sure to follow the proper format. Can you please help me locate where I went wrong?
Equations must be defined using Boolean equals. Second partial derivatives are not allowed on the left-hand-side of equations, you must convert your equation to a system of equations in first derivatives only (see the QuickSheet example).
You should also look at your boundary condition definitions carefully!
